U.S. patent application number 12/145263 was filed with the patent office on 2009-12-24 for system and method for terahertz imaging.
This patent application is currently assigned to GENERAL ELECTRIC COMPANY. Invention is credited to Michael Breit, Thorbjorn Christopher Buck.
Application Number | 20090314943 12/145263 |
Document ID | / |
Family ID | 41430242 |
Filed Date | 2009-12-24 |
United States Patent
Application |
20090314943 |
Kind Code |
A1 |
Breit; Michael ; et
al. |
December 24, 2009 |
SYSTEM AND METHOD FOR TERAHERTZ IMAGING
Abstract
A security inspection system is provided. The security
inspection system includes a source configured to transmit a beam
of radiation comprising a frequency of at least about 10 GHz. The
system also includes an optical system configured to focus the beam
of radiation on a sample. The system further includes at least one
detector configured to detect one or more reflected beams from
different locations of the sample in a focal plane of the optical
system and generate a corresponding output signal. The system also
includes a processor coupled to the at least one detector and
configured to reconstruct a three dimensional image of the sample
based upon the output signal.
Inventors: |
Breit; Michael; (Munchen,
DE) ; Buck; Thorbjorn Christopher; (Munchen,
DE) |
Correspondence
Address: |
GENERAL ELECTRIC COMPANY;GLOBAL RESEARCH
PATENT DOCKET RM. BLDG. K1-4A59
NISKAYUNA
NY
12309
US
|
Assignee: |
GENERAL ELECTRIC COMPANY
SCHENECTADY
NY
|
Family ID: |
41430242 |
Appl. No.: |
12/145263 |
Filed: |
June 24, 2008 |
Current U.S.
Class: |
250/341.1 ;
324/642 |
Current CPC
Class: |
G01N 21/3581
20130101 |
Class at
Publication: |
250/341.1 ;
324/642 |
International
Class: |
G01J 5/10 20060101
G01J005/10 |
Claims
1. An inspection system comprising: a source configured to transmit
a beam of radiation comprising a frequency of at least about 10
GHz; an optical system configured to focus the beam of radiation on
a sample, the optical system comprising a pinhole camera configured
to transmit one or more reflected beams; at least one detector
configured to detect one or more reflected beams from different
locations of the sample in a focal plane of the optical system and
generate a corresponding output signal; and a processor coupled to
the at least one detector and configured to reconstruct a three
dimensional image of the sample based upon the output signal.
2. (canceled)
3. The system of claim 1, wherein the optical system comprises at
least one mirror configured to focus the beam of radiation on to
the sample.
4. The system of claim 1, wherein the optical system comprises a
beamsplitter configured to split the beam of radiation transmitted
from the source and the one or more reflected beams from the
sample.
5. The system of claim 1, wherein the sample comprises luggage,
shoes, clothing, or a cardboard box.
6. The system of claim 1, wherein the source comprises a continuous
wave laser source, a backward wave oscillator source, a quantum
cascading laser source, a multiplier chain source, a gas laser
source, or other high-power source.
7. The system of claim 1, wherein the sample is configured to be
actuated in at least one of three dimensions relative to the
optical system to scan an entire volume of the sample.
8. The system of claim 1, wherein the optical system is configured
to be actuated in at least one of the three dimensions relative to
the sample to scan an entire volume of the sample.
9. The system of claim 1, wherein the processor is configured to
generate a plurality of two-dimensional images based upon the
output signal.
10. A method for manufacturing an inspection system comprising:
providing a source configured to transmit a beam of radiation
comprising a frequency of at least about 10 GHz; providing an
optical system configured to focus the beam of radiation on a
sample, the optical system comprising a pinhole camera configured
to transmit one or more reflected beams; providing at least one
detector configured to detect one or more reflected beams from
different locations of the sample in a focal plane of the optical
system and generate a corresponding output signal; and providing a
processor coupled to the at least one detector and configured to
generate a three dimensional image of the sample based upon the
output signal.
11. The method of claim 10, wherein said providing a source
comprises providing a continuous wave laser source, a backward wave
oscillator source, a quantum cascading laser source, a multiplier
chain source, a gas laser source, or other high-power source.
12. (canceled)
13. The method of claim 10, wherein said providing an optical
system comprises providing at least one mirror configured to focus
the beam of radiation onto the sample.
14. The method of claim 10, wherein said providing an optical
system comprises providing a beamsplitter configured to split the
one or more reflected beams from the sample.
15. The method of claim 10, comprising actuating the sample in at
least one of three dimensions relative to the optical system to
scan an entire volume of the sample.
16. The method of claim 10, further comprising actuating the
optical system relative to the sample to scan an entire volume of
the sample.
17. The method of claim 10, wherein said providing a processor
comprises reconstructing a plurality of two dimensional images
obtained from the at least one detector to generate the three
dimensional image.
Description
BACKGROUND
[0001] The invention relates generally to inspection systems and,
more particularly, to inspection systems employing terahertz
imaging.
[0002] A wide variety of inspection systems have been developed
that may be utilized in security applications, such as, but not
limited to, security screening of passenger luggage, packages,
and/or cargo. For example, inspection systems are employed at
various public or private installations, such as airports, for
screening persons, luggage, packages and cargo, to detect the
presence of contraband (e.g., weapons, explosives and drugs). Such
systems include metal detectors, X-ray based inspection systems,
nuclear magnetic resonance based inspection systems, nuclear
quadruple resonance based inspection systems, and so forth. In such
applications, acquired data and/or generated images may be used to
detect objects, shapes or irregularities which are otherwise hidden
from visual inspection and which are of interest to the screener.
However, these imaging and/or inspection systems have one or more
of various limitations such as low reliability in detecting
explosives and drugs (leading to high rates of false alarms),
health risk to screeners and those being screened due to exposure
to harmful radiation, long screening time (leading to decreased
throughput at checkpoints), and so forth.
[0003] Although many computed tomography (CT) based systems exhibit
an excellent probability of detection, these systems are
susceptible to high false alarm rates. A common reason for the
generation of a false alarm is that conventional CT sensors have
difficulty in distinguishing actual threat objects from harmless
objects since these objects may exhibit similar threat definitions
(for example, similar density and mass). Although there has been
continued effort to improve false alarm rates of explosives
detection systems employing CT technologies, for example,
improvement is still needed.
[0004] Furthermore, the aforementioned X-ray transmission systems
are not able to effectively detect materials (such as plastics or
plastic explosives), especially when shaped into objects of thin
cross-section, since they cause relatively small attenuation of
X-rays. On the other hand, some X-ray scatter systems are not able
to consistently identify threat material such as weapons,
explosives or drugs located deep inside an object.
[0005] Accordingly, there is a need for an inspection system that
can reliably detect threat material being located anywhere in an
examined object.
BRIEF DESCRIPTION
[0006] In accordance with an embodiment of the invention, an
inspection system is provided. The inspection system includes a
source configured to transmit a beam of radiation comprising a
frequency of at least about 10 GHz. The inspection system also
includes an optical system configured to focus the beam of
radiation on a sample. The inspection system further includes at
least one detector configured to detect one or more reflected beams
from different locations of the sample in a focal plane of the
optical system and generate a corresponding output signal. The
inspection system also includes a processor coupled to the at least
one detector and configured to reconstruct a three dimensional
image of the sample based upon the output signal.
[0007] In accordance with another embodiment of the invention, a
method for manufacturing an inspection system is provided. The
method includes providing a source configured to transmit a beam of
radiation comprising a frequency of at least about 10 GHz. The
method also includes providing an optical system configured to
focus the beam of radiation on a sample. The method further
includes providing at least one detector configured to detect one
or more reflected beams from different locations of the sample in a
focal plane of the optical system and generate a corresponding
output signal. The method also includes providing a processor
coupled to the at least one detector and configured to reconstruct
a three dimensional image of the sample based upon the output
signal.
[0008] These and other advantages and features will be more readily
understood from the following detailed description of preferred
embodiments of the invention that is provided in connection with
the accompanying drawings.
DRAWINGS
[0009] FIG. 1 is a schematic representation of an inspection system
including terahertz radiation in accordance with an embodiment of
the invention.
[0010] FIG. 2 is a diagrammatic illustration of an exemplary
application of the inspection system in FIG. 1.
[0011] FIG. 3 is a flow chart representing steps in a method for
manufacturing an inspection system in accordance with an embodiment
of the invention.
DETAILED DESCRIPTION
[0012] As discussed in detail below, embodiments of the invention
include a system and method for terahertz imaging. Generally, the
system and method may be used in a variety of terahertz imaging
and/or spectroscopy systems, such as for medical imaging,
industrial quality control, and security screening. Though the
present discussion provides examples in a context of security
screening, one of ordinary skill in the art will readily comprehend
that the application in other contexts, such as for medical imaging
and industrial quality control, is well within the scope of
embodiments of the invention.
[0013] It should be noted that reference is made herein to a
"sample" that is to be imaged or scanned. The use of the term
"sample" is not intended to limit the scope of the appended claims
and may broadly indicate a human, an animal, a sealed package,
luggage such as a briefcase or a suitcase, a carton, or a cargo
container that may be employed to carry an object of interest such
as explosives, drugs, weapons, or other contraband. In general, the
term may include any article, system, vehicle, or support in which
or on which contraband may be placed. Moreover, the subject may
refer to objects being examined for a defect via nondestructive
evaluation, carrier tissue in a tooth during dental imaging,
cancerous tissue in a body during medical imaging, and so
forth.
[0014] FIG. 1 is a diagrammatic illustration of an inspection
system 10 employing a radiation source 12 having a frequency of at
least about 10 GHz. In an exemplary embodiment, the source 12
includes at least one of a continuous wave laser source, a backward
wave oscillator source, a quantum cascading laser source, a
multiplier chain source, a gas laser source, or other high-power
source. Radiation beams 14 emitted from the source 12 are captured
by an optical system 16. The optical system 16 focuses the
radiation beams 14 on to a sample 18 to be examined. In one
embodiment, the optical system 16 includes at least one mirror
configured to focus the beams 14 onto the sample 18. Non-limiting
examples of the sample include luggage, shoes, clothing, or a
cardboard box. The radiation beams 14 are reflected from the sample
18 resulting in reflected beams 22. The reflected beams 22 that are
in a focal plane, referenced by numeral 23, of the optical system
16 are further incident upon a detector 24, while the reflected
beams 26 that are not in a focal plane, referenced by 27, are not
allowed to be incident upon the detector 24. It will be appreciated
that an array of detectors 24 may also be employed.
[0015] In a particular embodiment, the optical system 16 includes a
pinhole camera 25 that transmits the reflected beams 22 that are in
focus onto the detector and prevents the reflected beams 26 that
are out of focus from reaching the detectors 24. In another
embodiment, the optical system 16 includes a beamsplitter 17 that
splits the reflected beams 22, 24. A whole volume of the sample 18
may be scanned along a third dimension either by actuating the
sample relative to the optical system 16 or by actuating the
optical system relative to the sample 18. The actuation ensures
different locations within the sample are brought in focus
resulting in the detection of an entire volume of the sample 18.
The sample 18 and the optical system 16 may be actuated in at least
one of three dimensions referenced by numeral 31. The detector 24
detects the beams 22 to generate a corresponding output signal 32.
A processor 34 is coupled to the detector 24 to generate multiple
two dimensional images of different locations within the sample 18
based upon the output signal 32 and further reconstruct the two
dimensional images to generate a three dimensional image. It should
be noted that any suitable reconstruction algorithm known in the
art, may be employed to generate an image from the detector output
signal 32.
[0016] It should be noted that embodiments of the invention are not
limited to any particular processor for performing the processing
tasks of the invention. The term "processor," as that term is used
herein, is intended to denote any machine capable of performing the
calculations, or computations, necessary to perform the tasks of
the invention. The term "processor" also is intended to denote any
machine that is capable of accepting a structured input and of
processing the input in accordance with prescribed rules to produce
an output. It should also be noted that the phrase "configured to"
as used herein means that the processor is equipped with a
combination of hardware and software for performing the tasks of
embodiments of the invention, as will be understood by those
skilled in the art.
[0017] FIG. 2 is a schematic illustration of an exemplary
application of the inspection system 10. The inspection system 10
examines a shoe 52 that includes a ceramic knife 54 embedded within
a sole 56 of the shoe 52. The shoe 52 is scanned at different
depths to locate the knife 54. As described above, depths that lie
in a focal plane of the optical system 16 (FIG. 1) are incident on
the detector 24 (FIG. 1) generating multiple two dimensional images
and further reconstructed to produce a three dimensional image. As
illustrated herein, images 58, 60, 62 and 64 represent locations
within the shoe 52 at a depth of 0 mm, 5 mm, 10 mm, and 15 mm
respectively. The depth is measured from a top of the shoe 52.
Image 58 corresponds to a surface of the shoe 52 and is relatively
blurred, while as the shoe 52 is further scanned such that
locations within the shoe 52 at a depth of 5 mm are in focus, a
clearer image 60 of the shoe 52 is produced showing ripples 68 on
the sole 56. Similarly, the ripples 68 get blurred in the image 62
at a depth of 10 mm and furthermore, the image 64 at a depth of 15
mm starts to focus on a location 70 of the knife 54.
[0018] FIG. 3 is a flow chart representing steps in a method for
manufacturing an inspection system. The method includes providing a
source configured to transmit a beam of radiation comprising a
frequency of at least about 10 GHz in step 102. In one embodiment,
a continuous wave laser source, a backward wave oscillator source,
a quantum cascading laser source, a multiplier chain source, a gas
laser source, or other high-power source is provided. An optical
system is provided in step 104 to focus the beam of radiation on a
sample to be examined. In a particular embodiment, at least one
mirror is provided that focuses the beam of radiation onto the
sample. In another embodiment, a beamsplitter is provided that
splits one or more reflected beams from the sample. At least one
detector is provided in step 106 to detect one or more reflected
beams from different locations of the sample in a focal plane of
the optical system and generate a corresponding output signal. A
processor is provided in step 106 and is coupled to the at least
one detector to generate a three dimensional image of the sample
based upon the output signal. In one embodiment, the processor
reconstructs multiple two dimensional images obtained from the at
least one detector, to generate the three dimensional image. In an
exemplary embodiment, the sample is actuated in at least one of
three dimensions relative to the optical system to scan an entire
volume of the sample. In another embodiment, the optical system is
actuated relative to the sample to scan an entire volume of the
sample.
[0019] The various embodiments of a system and method for
inspection of threat material in objects as described above thus
provide a convenient, cost effective and efficient means to prevent
security incidents from occurring. Three dimensional tomographic
imaging with harmless terahertz radiation provide increased
detection capability for objects such as, but not limited to,
metal, ceramic, weapons, special nuclear materials, and explosives.
The technique enables determining a three dimensional size of a
defect by increasing resolution in the third dimension.
Advantageously, terahertz radiation is also non-ionizing and not
hazardous as compared to X-ray radiation. The system and technique
described above also facilitate reduction of false alarms,
consequently reducing expensive and time consuming secondary
inspections of objects.
[0020] It is to be understood that not necessarily all such objects
or advantages described above may be achieved in accordance with
any particular embodiment. Thus, for example, those skilled in the
art will recognize that the systems and techniques described herein
may be embodied or carried out in a manner that achieves or
optimizes one advantage or group of advantages as taught herein
without necessarily achieving other objects or advantages as may be
taught or suggested herein.
[0021] Furthermore, the skilled artisan will recognize the
interchangeability of various features from different embodiments.
For example, the use of a backward wave oscillation source
described with respect to one embodiment can be adapted for use in
inspection of shoes described with respect to another. Similarly,
the scanning in a third dimension may be achieved either by
scanning the object along the third dimension or by scanning the
optical system along the third dimension. Further, the various
features described, as well as other known equivalents for each
feature, can be mixed and matched by one of ordinary skill in this
art to construct additional systems and techniques in accordance
with principles of this disclosure.
[0022] While the invention has been described in detail in
connection with only a limited number of embodiments, it should be
readily understood that the invention is not limited to such
disclosed embodiments. Rather, the invention can be modified to
incorporate any number of variations, alterations, substitutions or
equivalent arrangements not heretofore described, but which are
commensurate with the spirit and scope of the invention.
Additionally, while various embodiments of the invention have been
described, it is to be understood that aspects of the invention may
include only some of the described embodiments. Accordingly, the
invention is not to be seen as limited by the foregoing
description, but is only limited by the scope of the appended
claims.
* * * * *